CD56 AIDS IN THE IDENTIFICATION OF TUMORS WITH NEUROENDOCRINE DIFFERENTIATION AND IN THE IDENTIFICATION OF NATURAL KILLER CELL LINEAGE IN A SUBSET OF LYMPHOMAS. IT IS EXPRESSED IN TUMORS WITH NEUROENDOCRINE DIFFERENTIATION LIKE SMALL CELL LUNG CARCINOMA AND NEURAL-DERIVED TUMORS OR NATURAL KILLER CELL LINEAGE (SUBSET OF LYMPHOMAS). IN NORMAL SMALL INTESTINE, THE GANGLION CELLS IN THE MUSCLE WALL AND NERVES WILL SHOW STRONG STAINING. SCATTERED LYMPHOCYTES MAY ALSO BE POSITIVE.

CD45 EXPRESSION IS VERY SPECIFIC AND QUITE SENSITIVE FOR CELLS OF HEMATOLYMPHOID LINEAGE. IT HELPS IN DISTINGUISHING LYMPHOMA / LEUKEMIA FROM OTHER NEOPLASMS. THE MAIN EXCEPTION IS CLASSICAL HODGKIN LYMPHOMA, IN WHICH CD45 EXPRESSION IS ABSENT.